The performance criteria of surgical needles can be measured in three interrelated ways. First, needle sharpness is necessary to reduce penetration resistance between needle and tissue. Greater sharpness lessens the external force required to embed the needle into tissue during surgery. Second, it is desirable to improve the needle cross-section so that the tissue opening, more commonly referred to as the wound opening site, is also reduced. As suspected, with improved penetration, the wound opening is also reduced. Third, when wound opening size is reduced, this will generally minimize the amount of tissue distortion during penetration of the needle.
With improved penetration, reduced wound opening and minimized tissue distortion, tissue apposition is generally improved. As a result, finer and more approximate surgery is possible. Thus, with improved needle sharpness, it is increasingly possible to perform more specialized surgery, especially in such highly refined areas as ophthalmology, microsurgery or plastic surgery.
Generally, it has been found that the optimal needle point must have a sharply tapered end, as well as a reduced cross-section. With a sharply tapered end, it is possible to achieve penetration without maximum tissue distortion. The reduced cross-section in this case will also reduce the wound opening area. It has been found that needles triangular in cross-section have performed quite well in conjunction with tapered ends.
Nevertheless, even these triangular needles require refining in order to improve the previously stated needle sharpness criteria. That is, none of the generally triangular needles have acceptably improved all the criteria in order to configure an optimal needle. Triangular shaped cross-section needles usually sacrifice one criterion for an increased benefit in another criterion.
What is needed, therefore, is a needle with improved sharpness which also reduces penetration resistance, as well as reducing wound opening area and minimizing tissue distortion. With this optimized needle cross-section, improved tissue apposition is possible, and highly refined surgery is generally more likely. In some instances, certain optimized needle cross-sections will prove useful in highly refined ophthalmic surgery. On the other hand, similar configurations with different curvatures in the needle will be useful for microsurgery and other general surgery within the body.